Depth-of-field is very important in portraits because a shallow one allows you to isolate the subject and separate it from the background, concentrating the viewer's attention. To achieve this you need to shoot with a wide open aperture, but some lenses have wider apertures than others. Then there is the digital problem. With SLRs you get around half a stop more depth of field than you might expect, which isn't a killer, but still a slight drawback. If you are using a compact digital, which have a much smaller sized CCD, then an aperture of f/2.8 suddenly produces the depth of field sharpness of something like f/16. Now that's useless for portraits as it means everything behind the subject will be in focus. That's one reason why compacts are aimed at point and shoot snappers rather than photography enthusiasts. This PSP X1 tutorial aims to reduce the depth of field in a graduated fashion to help the subject stand out from the background.
This is the original image which shows lots of depth-of-field and unnecessary clutter behind the subject. Right click the image and select Save Target As to download a bigger version to try this tutorial.
Here you can see where the effect is needed behind the subject as it is marked in red. That area will become blurred, whereas the foreground, girl and chair will all remain in focus.
DEPTH OF FIELD
This is the amount of the picture, from front to back, that is in sharp focus. Essential for landscapes, but entirely distracting for portraits.
The reason for using the gradient on a layer mask is so that the blur effect is applied gradually up the image, so that the further away the background becomes, the more out of focus it is. You can experiment with the gradient in the Edit button to determine where it starts and stops.
The figure is cut out and the gaps filled in rather than simply the background being selected, because otherwise the Gaussian Blue filter will blur from outside the selection where the figure is, onto the background, resulting in a strange halo effect.
By necessity, the screenshots on the page are reduced in size, so click on any of them, including the final image, to see them at full size.
THE STEP BY STEP
1. When the subject is stood in the picture, as opposed to being cut off by it, then introducing a shallow depth of field is harder, and needs to be done in a graduated fashion. Also, because of the way the Gaussian Blur filter works, it will pick up the subject, even if they are outside the selection, giving an unwanted halo effect. So, to start, load the picture and zoom in to 150%. Click on the Freehand Selection tool and set it to the Point to Point in the Selection type box.
2. What we are going to do now is mark around the subject, the chair and table right at the front of the picture. So, start off on one foot, and mark around the figure. Hold down the Ctrl key to switch to subtract mode and remove the area inside the arms. Then press on the Shift key to start adding the chair and table leg. You will also need to remove the areas that you can see through the chair from the selection as well. When complete, go to Selections> Modify > Contract and set it by 2 pixels. Then go to Selections > Modify> Inside/Outside feather, and select Inside by 2 pixels.
3. Go to Edit/ Cut to remove the selected area. A shadow the colour of the current background colour will appear. Now go to Edit and select Paste as New Layer. The new layer with the figure and chair will appear, but annoyingly, not in the original position. Click on the Move tool and move it carefully back over the original position. You may see a slight shadow or halo, which is because of the feathering. Rename the new layer, Figure. Now click on the Eye symbol on the Figure layer to make it invisible, and click on the background layer to select it.
4. Click on the Clone brush and set it to 100% Opacity and 0% Hardness. Start to clone in from all around the black area, filling inwards. You should fill the cut out areas and not affect the original background that is still visible. You don't have to fill the entire figure in, just 10 pixels inside the black area is plenty. The only important part of the chair on the right is where it juts against the table. Ensure that you clone into the cut out area here without affecting the table.
5. Right click on the background layer and select Duplicate. Call this the Blur layer. Remove the selection. Now go to Layers> New Mask Layer> Show All. This incomprehensible command will add a layer mask to the blur layer, while creating a grouping out of it. Click on the mask to select it then click on the Flood Fill tool. Set the colour to black then click on the Gradient tab under the colour in the Materials palette. Select the black to white gradient. Click on the gradient itself to bring up the properties and move the pointer line if necessary so that it is pointing upwards, from black to white. Click on the Edit button to reveal the Gradient properties. Set the left marker to 20%, the middle to 25% and the right marker to 50%.
6. Click on Close to shut this window then click on OK to select the Gradient. Click on the Eye symbol for the background layer so you can see the effect easily. Click anywhere the Mask itself with the Flood fill tool to apply the gradient. Now, click on the Blur layer and go to Adjust> Blur> Gaussian Blur. Enter a radius of 5 pixels. Turn the visibility of the background layer and the Figure layer back on and you should now see the focus fade into the background, while the figure remains sharp. Merge the layers to finish.